几何变换

1|0安装glm

GLM（类似numpy），是一个只有头文件的库，下载下来源码把里面的glm文件夹复制到VS的include目录下就可以了
然后类似这么调用：

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

2|0初始化变换矩阵

glm::mat4 trans = glm::mat4(1.0f)

旋转的话：
trans = glm::rotate(trans, glm::radians(90.0f), glm::vec3(0.0, 0.0, 1.0));
其中，第一个参数是矩阵，下面继续写的话继续直接连乘，第二个参数是要用到弧度，然后radians把角度转弧度，第三个参数是绕哪个轴旋转，这是绕z轴
scale的话：
trans = glm::scale(trans, glm::vec3(0.5, 0.5, 0.5));
第一个参数与上面的旋转连乘了，第二个是因为0.5也要用glm的vec才认

3|0vertexshader

uniform一个transform矩阵
gl_Position的vec4坐标前乘变换矩阵transform
纹理坐标不用变，变换了之后纹理坐标还能对应上

4|0uniform修改

获取uniform在shader里的位置，然后

unsigned int transformLoc = glGetUniformLocation(myshader.ID, "transform");

在渲染循环里，画图之前：

glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(trans));

变换的时候uniform的修改一定要写在渲染循环里

5|0在渲染循环里变换

把初始化和translate、scale、rotate等都写在渲染循环里，不每次都初始化的话矩阵会一直随时间变
trans = glm::rotate(trans, (float)glfwGetTime(), glm::vec3(0.0, 0.0, 1.0));

#include<glad/glad.h>
#include<GLFW/glfw3.h>
#include<iostream>
#include<Shader.cpp>
#define STB_IMAGE_IMPLEMENTATION
#include<stb_image.h>
#include<glm/glm.hpp>
#include<glm/gtc/matrix_transform.hpp>
#include<glm/gtc/type_ptr.hpp>
void framebuffer_size_callback(GLFWwindow* window, int width, int height) 
{
	glViewport(0, 0, width, height);
}
void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_KP_ENTER) == GLFW_PRESS or glfwGetKey(window, GLFW_KEY_ENTER) == GLFW_PRESS or glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}
int main()
{
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	//创建窗口对象
	GLFWwindow* window = glfwCreateWindow(800, 600, "LJHyyds", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	//初始化GLAD管理指针，加载系统OpenGL函数指针
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to init GLAD" << std::endl;
		return -1;
	}
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
	Shader myshader("shader.vs", "shader.fs");
	float vertices[] = {
		 0.5f,  0.5f, 0.0f,  1.0f, 1.0f,//右上
		 0.5f, -0.5f, 0.0f,	 1.0f, 0.0f,//右下
		-0.5f,  0.5f, 0.0f,	 0.0f, 1.0f,//左上
		-0.5f, -0.5f, 0.0f,  0.0f, 0.0f,//左下
	};
	int indices[] = {
		0, 1, 2,
		1, 2, 3
	};
	unsigned int VBO, VAO, EBO, texture;
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);
	glGenTextures(1, &texture);
	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);
	glBindTexture(GL_TEXTURE_2D, texture);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);	//第一个是类型，第二个是大小，第三个是数据
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
	glEnableVertexAttribArray(1);
	int width, height, nrChannels;
	unsigned char *data = stbi_load("container.jpg", &width, &height, &nrChannels, 0);
	if (data)
	{
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
		glGenerateMipmap(GL_TEXTURE_2D);
	}
	else
	{
		std::cout << "Failed to load texture" << std::endl;
	}
	stbi_image_free(data);
	unsigned int transformLoc = glGetUniformLocation(myshader.ID, "transform");
	myshader.use();
	while (!glfwWindowShouldClose(window))
	{
		processInput(window);
		glClearColor(0.0f, 0.5f, 1.0f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		glm::mat4 trans = glm::mat4(1.0f);
		trans = glm::translate(trans, glm::vec3(0.5, 0.0, 0.0));
		trans = glm::rotate(trans, (float)glfwGetTime(), glm::vec3(0.0, 0.0, 1.0));
		glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(trans));
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	//关闭窗口
	glfwTerminate();
	return 0;
}

shader.vs

#version 330 core
layout (location=0) in vec3 aPos;
layout (location=1) in vec2 aTexCoord;

out vec2 TexCoord;

uniform mat4 transform;

void main()
{
	gl_Position = transform * vec4(aPos, 1.0);
	TexCoord = aTexCoord;
}
``

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__EOF__

本文作者：Liujiahang
本文链接：https://www.cnblogs.com/IamIron-Man/p/16614063.html
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